Coronary microvascular dysfunction (CMD) is proposed to be a contributor to the signs and symptoms of myocardial ischaemia, which results from a limited microvascular vasodilator capacity under vasodilator stimuli (Crea, Camici, & Bairey Merz, 2014). Coronary flow reserve (CFR), quantified as the ratio of hyperaemic to rest myocardial blood flow, is a functional measure of large-and small-vessel ischaemia, and in the absence of overt coronary artery disease (CAD), is a marker of CMD (Taqueti et al.,